The Acne and the scarring went long before the pigmentation did - it was hyperpigmentation known as melasma, a side effect of some medication, Minocin included (needless to say no doctor warned be about this side effect whcih ended up being more upsetting in the long run than the Acne ever was...)
I didnt really get much pigmentation from the scarring, probably because I was using rosehip oil all along and not just after the fact. After starting to take MSM it was about 3 weeks to a month before my face was totally clear. MSM by itself didnt fade the melasma pigmentatioon that I was left with - I eventually faded that completely by eating a diet low in copper, and detoxing my liver of excess copper by taking MSM along with zinc and vitamin C. The pigmentation you might get from Acne scars seems to be different, and easier to get rid of than the melasma pigmentation, which I now believe to be caused by a build up of copper in the system.